Submission #1103862

#	Time	Username	Problem	Language	Result	Execution time	Memory
1103862		KasymK	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	375 ms	24988 KiB

commuter_pass

#include "bits/stdc++.h"
using namespace std;
#define ff first
#define ss second
#define all(v) v.begin(), v.end()
#define ll long long
#define pb push_back
#define pii pair<int, int>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define tr(i, c) for(auto i = c.begin(); i != c.end(); ++i)
#define wr puts("----------------")
template<class T>bool umin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool umax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
const int N = 1e5+5;
const ll INF = 1e18;
vector<pii> adj[N];
ll d[N][3], ds[N], dt[N];
int n, m, s, t, u, v;

bool check(int x, int y, int w, bool why){
    if(why)
        return ds[y]+w+dt[x]==ds[t];
    else
        return ds[x]+w+dt[y]==ds[t];
}

void dij(int s){
    for(int i = 1; i <= n; ++i)
        dt[i] = INF;
    priority_queue<pli, vector<pli>, greater<pli>> pq;
    dt[s] = 0;
    pq.push({0, s});
    while(!pq.empty()){
        int x = pq.top().ss;
        ll val = pq.top().ff;
        pq.pop();
        if(dt[x] != val)
            continue;
        tr(it, adj[x]){
            int a = it->ff, w = it->ss;
            if(umin(dt[a], dt[x]+w))
                pq.push({dt[a], a});
        }
    }
}

ll solve(bool why){
    for(int i = 1; i <= n; ++i)
        for(int j = 0; j < 3; ++j)
            d[i][j] = INF;
    using node = tuple<ll, int, int>;
    // dttance, node, type
    priority_queue<node, vector<node>, greater<node>> pq;
    d[u][0] = 0;
    pq.push({0, u, 0});
    while(!pq.empty()){
        int x, type;
        ll val;
        tie(val, x, type) = pq.top();
        pq.pop();
        if(d[x][type] != val)
            continue;
        if(type<2 and umin(d[x][type+1], d[x][type]))
            pq.push({d[x][type+1], x, type+1});
        tr(it, adj[x]){
            int y = it->ff, w = it->ss;
            if(type==0 and umin(d[y][0], d[x][0]+w))
                pq.push({d[y][0], y, 0});
            else if(type==1 and check(x, y, w, why) and umin(d[y][1], d[x][1]))
                pq.push({d[y][1], y, 1});
            else if(type == 2 and umin(d[y][2], d[x][2]+w))
                pq.push({d[y][2], y, 2});
        }
    }
    return d[v][2];
}

int main(){
    scanf("%d%d%d%d%d%d", &n, &m, &s, &t, &u, &v);
    for(int i = 1; i <= m; ++i){
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        adj[a].pb({b, c});
        adj[b].pb({a, c});
    }
    dij(s);
    for(int i = 1; i <= n; ++i)
        ds[i] = dt[i];
    dij(t);
    printf("%lld\n", min(solve(0), solve(1)));
    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:80:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |     scanf("%d%d%d%d%d%d", &n, &m, &s, &t, &u, &v);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:83:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   83 |         scanf("%d%d%d", &a, &b, &c);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45